echo "Checking tape drive: $TAPE_DRV ..." mt -f $TAPE_DRV rewind > /dev/null 2>&1 if [ $? = 0 ] then echo "... is OK" go_code=0 else echo "... is not working - ABORTING BACKUP" go_code=1 bstatus="was ABORTED - NO TAPE IN DRIVE" fi if [ "${go_code}" = "0" ] ................... find . ( -type d -a -exec chmod 775 {} ; ) -o ( -name *.htm* -a -exec chmod 664 {} ; ) -o ( -name *.css -a -exec chmod 664 {} ; ) ============================================= function pinghost() { ping -c 1 $1 > /dev/null 2>&1 } while pinghost A do sleep 10 done ======================= This means connect to port 80 (HTTP) of the host specified in the function argument and execute the command GET /; then scan the output for the string "". If it is found, return 0 (success), otherwise return non-zero (failure). The options to grep mean "suppress all visible output". function pingservice() { echo "GET /" | nc $1 80 | grep -qs "" } ======================= monitor other host service FLAG=1 if ! rexec A ps -e | grep -v grep | grep -qs httpd ; then rexec A apachectl graceful sleep 1 if pingservice A ; then FLAG=0 fi fi if [ FLAG==1 ] ; then rexec A ifconfig eth0 down apachectl graceful ifconfig eth0:0 192.168.31.1 up fi ======================= grep URLs egrep -o '(((http(s)?|ftp|telnet|news|gopher)://|mailto:)[^\(\)[:space:]]+)' logfile ----------------------- email addresses egrep -o '\@/:[:space:]]+\>@[a-zA-Z_\.]+?\.[a-zA-Z]{2,3}' somefile senders from an email archive and sort into a file of unique addresses: grep '^From: ' huge-mail-archive | egrep -o '\@/:[:space:]]+\>@[a-zA-Z_\.]+?\.[a-zA-Z]{2,3}' | sort | uniq > email.addresses ----------------------- grep in colors grep --color=always "regexp" myfile | less -R ----------------------- shade of green: GREP_COLOR=32; export GREP_COLOR; grep pattern myfile